Chapter 384 Emphysema and Overinflation
Localized Obstructive Overinflation
When a ball-valve type of obstruction partially occludes the main stem bronchus, the entire lung becomes overinflated; individual lobes are affected when the obstruction is in lobar bronchi. Segments or subsegments are affected when their individual bronchi are blocked. Localized obstructions that can be responsible for overinflation include foreign bodies and the inflammatory reaction to them, abnormally thick mucus (cystic fibrosis, Chapter 395), endobronchial tuberculosis or tuberculosis of the tracheobronchial lymph nodes (Chapter 207), and endobronchial or mediastinal tumors. When most or all of a lobe is involved, the percussion note is hyperresonant over the area, and the breath sounds are decreased in intensity. The distended lung can extend across the mediastinum into the opposite hemithorax. Under fluoroscopic scrutiny during exhalation, the overinflated area does not decrease, and the heart and the mediastinum shift to the opposite side because the unobstructed lung empties normally.
Unilateral Hyperlucent Lung
Unilateral hyperlucent lung can be associated with a variety of cardiac and pulmonary diseases of children, but in some patients, it occurs without demonstrable underlying active disease. More than half the cases follow one or more episodes of pneumonia; a rising titer to adenovirus (Chapter 254) has been documented in several children. This condition can follow bronchiolitis obliterans and can include obliterative vasculitis as well, accounting for the greatly diminished perfusion and vascular marking on the affected side.
